Dual-chamber chromatographic cartridge

ABSTRACT

A chromatography cartridge with a packed bed is manufactured from an inner and outer chamber, the inner chamber being in an insert that is slidable into the outer chamber with openings in each such that a slurry that is originally placed in the interior of the outer chamber flows into the inner chamber as the parts are being pressed into each other. During the assembly, the particles in the slurry are compressed to fill the smaller volume of the inner chamber and excess liquid is discharged through ports in both chambers. The construction allows for a highly precise and reproducible column filling process with a minimum of steps and operator intervention and thereby low cost and reduced error.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention resides in the field of laboratory apparatus forchromatographic separations of liquid samples. This invention isparticularly concerned with packed-bed column cartridges and theirmethod of manufacture.

2. Description of the Prior Art

Packed-column chromatography is widely used in clinical laboratories andresearch laboratories by virtue of its ability to separate components ofliquid samples from many sources and for many reasons. As both ananalytical tool and a diagnostic tool, packed-column chromatographyoffers a means of providing rapid determinations with a minimum ofeffort and sample preparation. As in all analytical and diagnosticmethods, the value of packed-column chromatography is greatest when alarge number of samples are to be analyzed under the same criteria orfor comparison with each other or with a standard. The optimalpacked-column chromatography system is therefore one that producesseparations quickly and in a reproducible and reliable manner. Thisrequires standardized conditions which include a high degree of controlover the packing volume, the packing density and the flow pattern of thesample and carrier liquid through the packing. These qualities are allenhanced when there is minimal opportunity for user error.

The need for speed, uniformity and reliability has led to thedevelopment of column cartridges or pre-packaged disposable columns,which are manufactured by mass production, purchased in bulk, and usedeither once or a limited number of times before being discarded. The useof cartridges that are packed by the manufacturer sharply reduces theopportunity for user error, and offers the standardization anduniformity that comes with high-volume manufacture and mass productiontechniques. Nevertheless, prepackaging shifts the error to themanufacturing process, where opportunities for error and variabilitystill exist. Such factors as the inattentiveness of individuals in themanufacturing plant and changes of manufacturing personnel can introducenonuniformities into the product, and in any event, the cost of laborremains a factor, particularly when a precision product is sought.

SUMMARY OF THE INVENTION

The present invention resides in a dual-chamber chromatography cartridgein which an outer chamber is designed to allow sliding entry of an innerchamber having an open end and a smaller volumetric capacity than theouter chamber, and one or both of the chambers has a liquid dischargeport that allows passage of liquid while blocking passage of solidparticles. The cartridge is thus packed and assembled by charging theouter chamber with a slurry of solid particulate packing material in acarrier liquid, then inserting the inner chamber into the outer chamberand sliding the inner chamber into the full depth of the outer chamberto force the slurry into the interior of the inner chamber whilecompressing the particulate material within the inner chamber. Byselecting a volume of slurry that contains sufficient particulatematerial to fill the interior of the inner chamber when the particulatematerial is packed and no more, and by allowing any excess carrierliquid to escape through the discharge port while the particulatematerial is being packed, the inner chamber upon full insertion will bedensely packed with the particulate material in a uniform and highlycontrolled manner by two simple steps—charging the outer chamber withthe slurry and inserting the inner chamber to its full depth. Thisreduces the number of steps in the packing process, allows the use ofautomated packing procedures with precisely controlled pressures, flowrates, and other operating conditions, and results in a finishedcartridge that is ready to use with a high degree of user confidence andreliability and low cost. The present invention thus resides in aprocess for manufacturing a packed-bed chromatography cartridgeutilizing the inner and outer chambers and a slurry of the packingmaterial, and in the combination of components that constitute thecartridge. Further objects, features, and advantages of the inventionwill be apparent from the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the components of a cartridge inaccordance with the present invention.

FIG. 2 is a cross section of two of the three components of FIG. 1 inpartially assembled configuration.

FIG. 3 is a cross section of the same components as FIG. 2 except fullyassembled.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The inner and outer chambers of the cartridges of this invention canvary widely in size and configuration, although preferably both arecylindrical with circular cross sections. The inner chamber will beselected with an axial length and cross-sectional area that are suitablefor the chromatographic separations to be performed in the cartridge.These dimensions will therefore vary according to the size of the sampleto be separated or analyzed, the particle size and volume of the packingmaterial, and any other parameters of the separation, and it will bebeneficial for a supplier to offer a range of sizes. The ratio of thecross-sectional area of the interior of the inner chamber to that of theinterior of the outer chamber can for example range from about 0.05 toabout 0.5. The volume of the inner chamber, and hence the bulk volume ofthe separation medium in the finished cartridge, can for example rangefrom about 0.5 mL to about 50 mL, or preferably from about 1 mL to about25 mL. Likewise, the length of the inner chamber can for example rangefrom about 1.0 cm to about 20 cm, or preferably from about 3 cm to about10 cm, and the length-to-diameter ratio of the interior of the innerchamber can for example range from about 1.25 to about 25, or preferablyfrom about 1.4 to about 10. In preferred embodiments of the invention,the inner and outer chambers are of equal or approximately equal length.

The packing material is supplied as a slurry to facilitate the placementof the material in the outer cylinder and also to facilitate the passageof the material from the outer cylinder into the inner cylinder as thetwo cylinders are pressed together. The slurry will contain an excess ofcarrier liquid to improve the flowability of the particles, and theexcess liquid will be discharged as the particles are compressed into apacked bed. The volume of the slurry when first placed in the interiorof the outer cylinder will thus be greater than the volume of theinterior of the inner cylinder and likewise greater than the finalvolume of the packed bed. The slurry volume may for example be about120% or more of the final packing volume, preferably about 150% or more,and most preferably about 200% or more. The outer chamber will be sizedto accommodate this slurry volume, preferably with excess space so thatthe slurry will occupy only a portion of the outer chamber. A preciselydetermined volume of slurry can then be added, and the volume adjustedas needed for different quantities of carrier liquid relative to thesuspended particles. The same outer cylinder can be used with innercylinders of different sizes and hence different slurry and particlevolumes.

The particles that form the packed bed are referred to herein as“solid.” This term is used in the present specification and claims toinclude both rigid particles and deformable resilient particles, and ingeneral any particles that are known to be useful as a stationary phasefor chromatographic separations. The term “packing volume” is usedherein to denote the bulk volume occupied by a mass of particles thathas been compressed to full packing density, i.e., to the point wherethe particles are in full contact and not movable either by agitation orby the flow of liquid across the bed. The remaining carrier liquid willoccupy the interstitial spaces between the packed particles.

As the slurry is compressed and the particles packed, excess carrierliquid is discharged through a discharge port in one or both of thechambers. Preferably, the inner chamber has a discharge port, and mostpreferably, both the inner and outer chambers have discharge ports. Whentwo ports are present, they will serve as inlet and outlet ports,respectively, for the elution buffer in a chromatographic separation asthe separation is being performed in the packed cartridge. The port, orports when two are present, are configured to allow the passage ofcarrier liquid but to block the passage of the particles, therebyallowing the particles to pack to full packing density while the chambercylinders are pressed together and the excess liquid is beingdischarged. To thus retain the particles while passing the liquid, theports will be either substantially smaller than the particles or willcontain particle blocking members such as frits, filters, mesh disks,and the like. The frits, filters or disks can reside inside the portsthemselves or can be placed over the port openings.

While the invention is susceptible of a variety of physicalconfigurations, the novel features of the invention that are common toall such configurations can be understood by a detailed review of oneexample. Such an example is shown in the attached drawings and describedbelow.

The perspective view of FIG. 1 shows three components of an illustrativecartridge, the components spatially separated for ease of viewing. Thecomponents include a cylinder 11, an insert 12, and an end cap 13. Thecylinder 11 is closed by a floor 14 at the bottom and open at the top15, with a discharge port 16 extending downward from the floor. Theinterior of the cylinder 11 serves as the outer chamber of thecartridge. The insert 12 includes a smaller cylinder 17 whose interiorserves as the inner chamber of the cartridge. The smaller cylinder 17has an open bottom (not visible in this Figure) and a roof or top 18that is closed except for a discharge port 19 at its center andextending upward. Both the lower discharge port 16 and the upperdischarge port 19 in this embodiment are shaped as components ofLUER-LOK® fittings, although any connective fittings can be used thatare designed to provide fluid-tight connections to transfer tubing or toother ports in a full chromatographic apparatus. The insert has a baseflange 21 and centering ribs 22 symmetrically arranged around thesmaller cylinder 17 to center the smaller cylinder inside the largercylinder 11. The end cap 13 secures the insert inside the largercylinder 11 by pressing against the upper edges of the centering rubs 22and engaging, i.e., hooking over, a skirt 23 at the top of the largercylinder 11 that encircles the outer side of the opening 15. Notches 24in the inner rim of a central opening 25 of the end cap engage the outercorners of shoulders 26 in the centering ribs of the insert for furthersecurement and stabilization.

The axial cross sections of FIGS. 2 and 3 show the larger cylinder 11and the insert 12, both taken along the aligned centerlines of each andin the planes of two opposing centering ribs 22. The end cap 13 is notshown in these Figures. Both Figures do however show two frits, one 31on the floor of the larger cylinder to block the entry of particles intothe lower discharge port 16 from the interior of the larger cylinder 11,and the other 32 placed inside the interior of the smaller cylinder 17of the insert 12 where it blocks the entry of particles to the upperdischarge port 19 from the interior of the smaller cylinder 17. In theview shown in FIG. 2, a volume of slurry 33 has been placed in thelarger cylinder 11, in the which the discharge port 16 is closed with amale LUER-LOK® cap, followed by placement of the insert 12 a shortdistance into the interior of the larger cylinder 11 with the open endsof both cylinders facing each other. The insert 12 is then pusheddownward into the larger cylinder 11 applying pressure to the upper endof the insert as indicated by the arrows 34, and the slurry is forcedinto the interior of the smaller cylinder 17 of the insert 12.

The resulting configuration is shown in FIG. 3 in which particles of theslurry have been retained inside the interior of the smaller cylinder 17where they form a packed bed 35. The packed bed 35 is smaller in volumethan the slurry, since it contains the particles fully packed, withexcess carrier liquid having been expelled through the discharge port 16as indicated by the arrow 36.

Both solid particles and carrier liquid are prevented from entering theannular space between the two cylinders and between the centering ribs22 by the base flange 21. This flange is visible in FIGS. 2 and 3 onlyby its lower surface 38, since these Figures are cross sections takenthrough a plane that includes the centering ribs. The base flange 21 ismore readily visible in FIG. 1, where the outer edge 41 of the baseflange is visible. This outer edge forms a sliding fluid-tight sealagainst the inner wall of the interior of the larger cylinder 11 toprevent passage of both liquid and solid. To facilitate the seal whileallowing the insert to be slid into place, the flange or the entireinsert can be manufactured from a material that is relatively rigidcompared to the larger cylinder 11. The relatively soft larger cylinderwill thus be slightly deformed during insertion of the insert by theoutward pressing force of the flange edge 41 against the cylinder wall.

The foregoing is offered for purposes of illustration. Furthervariations, modifications, and substitutions that fall within the scopeof the invention will be readily apparent to those skilled in the art.

1. A chromatography cartridge comprising: an outer chamber having alongitudinal axis, an open first end, and a second end containing aliquid discharge port adapted to allow passage of liquid while blockingpassage of solid particles, said outer chamber having an internal crosssection that is constant along said longitudinal axis, and an innerchamber having an open first end and a second end containing a ventport, said inner chamber slidably receivable in said outer chamber byinsertion of said open first end of said inner chamber through said openfirst end of said outer chamber, said inner chamber having a smallervolumetric capacity than said outer chamber.
 2. The chromatographycartridge of claim 1 further comprising sealing means between said innerand outer chambers for blocking liquid passage into regions between saidinner and outer chambers during insertion of said inner chamber.
 3. Thechromatography cartridge of claim 1 wherein said inner and outerchambers are both circular cylinders.
 4. The chromatography cartridge ofclaim 1 wherein said liquid discharge port and said vent port arecoaxial with said longitudinal axis.
 5. The chromatography cartridge ofclaim 1 wherein said inner and outer chambers are of substantially equallength.
 6. The chromatography cartridge of claim 1 wherein the ratio ofthe cross sectional areas of said inner chamber to said outer chamber isfrom about 0.05 to about 0.5.
 7. The chromatography cartridge of claim 1wherein said vent port is adapted to allow passage of liquid whileblocking passage of solid particles.
 8. The chromatography cartridge ofclaim 1 wherein said liquid discharge port is adapted to allow passageof liquid while blocking passage of solids by a filter or a fritretained within or at the entry to said liquid discharge port.
 9. Aprocess for the manufacture of a chromatography cartridge containing aselected volume of solid particulate packing material at a selectedpacking volume, said process comprising: (a) charging a first chamberwith a slurry of said solid particulate packing material in a carrierliquid, the packing material in said slurry being of a quantity thatwhen fully packed fills said selected packing volume, said first chamberhaving a longitudinal axis, an open first end, and a second endcontaining a liquid discharge port adapted to allow passage of liquidwhile blocking passage of said solid particles, (b) joining a secondchamber to said first chamber, said second chamber having an open firstend, a second end containing a vent port adapted to allow passage ofliquid while blocking passage of said solid particles, and an internalcavity having a volume equal to said selected volume of solidparticulate packing material, by inserting said open first end of saidsecond chamber into said open first end of said first chamber, and (c)sliding said second chamber further into said first chamber, therebyforcing substantially all of said solid particulate matter plus at leasta portion of said carrier liquid into said second chamber through saidopen end of said second chamber while compressing said particulatematter in said second chamber to said packing volume and dischargingexcess carrier liquid through said liquid discharge port, said ventport, or both.
 10. The process of claim 9 wherein said slurry of step(a) contains sufficient carrier liquid that the volume of said slurry isgreater than or equal to 120% of said selected packing volume.
 11. Theprocess of claim 9 wherein said slurry of step (a) contains sufficientcarrier liquid that the volume of said slurry is greater than or equalto 150% of said selected packing volume.
 12. The process of claim 9wherein said slurry of step (a) contains sufficient carrier liquid thatthe volume of said slurry is greater than or equal to 200% of saidselected packing volume.
 13. The process of claim 9 wherein said firstand second chambers are of substantially equal length.
 14. The processof claim 9 wherein the ratio of cross sectional areas of said secondchamber to said first chamber is from about 0.05 to about 0.5.